JPH0136351Y2 - - Google Patents

Description

[Detailed description of the invention] (a) Industrial application field The present invention relates to a UHF tuner used in television receivers, VTRs, etc.

(b) Prior Art Generally, as shown in Fig. 1, a UHF tuner amplifies the received high frequency signal given from an input terminal 1 with a high frequency amplifier 2, and also connects an input tuning circuit 3, an interstage primary side tuning circuit 4, and an interstage secondary side tuning circuit 4. The local oscillation signal from the local oscillation circuit 7 and the interstage secondary side tuning circuit 5 are selected by the side tuning circuit 5, and in the mixing circuit 6, the local oscillation signal from the local oscillation circuit 7 and the interstage secondary side tuning circuit 5
The received high frequency signals are mixed and converted into intermediate frequency signals. In the figure, L ₁ , L ₂ , L ₃ , and L ₄ are resonant lines, D ₁ , D ₂ , D ₃ , and D ₄ are variable capacitance diodes, TR ₁ is a MOS field effect transistor, and TR _{2 is} a MOS field effect transistor.
is an oscillation transistor, C ₁ , C ₂ , C ₃ , and C ₄ are DC blocking capacitors, C ₅ is a feedback capacitor, and L ₅ and C ₆ are a capacitor and coil forming a low-pass filter. D ₅ is a mixing diode. The resonant line is
For example, to give a specific example of the interstage secondary side tuning circuit 5 as a representative example, as shown in FIG.
The other end is held by being connected to the variable capacitance diode _D3 , and the other end is held as shown in Fig. 3.
There is also one that is U-shaped and has both ends fixed to the printed circuit board 8. In the case of Figure 3,
The variable volume diode is attached to another part of the printed circuit board 8 and connected to the resonant line _L3 through the copper foil of the printed circuit board.

In FIG. 1, the high frequency signal is extracted to the mixing diode _D5 by the first pick-up line 9 to the interstage secondary side tuned circuit 5, while the local oscillation signal is extracted to the interstage secondary side tuned circuit 5 by the second pick-up line 10. Picked up from 7. The first and second pick-up lines 9 and 10 can both be used as lead wires of the mixing diode _D5 .

Now, the reception frequency is f, the local oscillation frequency is fl,
If the intermediate frequency is fi, then in the case of the superheterodyne reception method, the image frequency f±2
Since fi is converted to the same intermediate frequency fi as the intermediate frequency fi of the receiving frequency f, it will cause interference, so
It is necessary to remove this image frequency. For this purpose, a trap circuit may be provided at this frequency. This trap circuit is composed of a series circuit of L and C, where L is determined by the length of the pick-up line 9, and C is determined by the distance d between the pick-up line 9 and the resonant line _L3 . Therefore, L
can be changed by changing the length of the lead 9 of the diode _D5 , and C can be changed by changing the above-mentioned interval d, so by changing these L and C, the trap frequency can be changed.

In this way, the length of the first pick-up line 9,
The separation distance d between the first pickup line 9 and the resonant line _L3 forms a trap shown by the broken line (R) in FIG. This trap serves to remove image disturbances. A shows the response when receiving a certain channel of UHF, where f ₀ is the center frequency of the intermediate frequency signal, and f ₁ is the trap frequency. However, the frequency of this trap is determined by d as described above, but this d tends to vary due to assembly, making it difficult to ensure sufficient quality regarding image interference. In order to solve this problem, it has been proposed to interpose a spacer 11 between the resonant line _L3 and the first pick-up line 9 as shown in FIG. It has the disadvantage of causing major problems. In FIG. 5, 12 is a casing of the tuner, and 13 is a partition plate integrated with the tuner casing 12.

(c) Purpose of the invention The purpose of the invention is to provide a UHF tuner with a structure that allows the trap frequency to be held constant without any problems in tuner manufacture.

(d) Structure of the invention In this invention, a rib is provided on the resonant line to face the pick-up line, and by positioning the pick-up line using this rib, the distance between the pick-up line and the resonant line is kept constant. It is something.

(E) Embodiment As shown in Fig. 6, in the present invention, the resonant line L ₃
Since the rib 14 is provided on the rib 14 and the first pickup line 9 is brought into contact with the rib 14 as shown in FIG. 7, the distance d between the resonant line _L3 and the first pickup line 9 can be kept constant. The rib 14 is easily formed by cutting a part of the protrusion 15 provided on the upper part of the resonant line _L3 and bending the protrusion 15 in a right angle direction. The first pickup line 9 has a portion that is bent from a portion parallel to the resonant line _L3 toward the mixing diode _D5 ;
This bent portion is positioned by the projection. As shown in the figure, the first and second pick-up lines 9 and 10 may have a structure in which the lead wires of the mixing diode _D5 are covered with vinyl 16 and 17, and are different from the lead wires of the mixing diode _D5 . may be used. When implementing this invention,
Ribs of various shapes can be formed on the resonant line without being limited to the illustrated example.

(F) Effects of the invention According to the invention, the distance between the pick-up line that picks up the received high-frequency signal from the tuned circuit and the resonant line of the tuned circuit can be made constant, so that the trap frequency for trapping image disturbance can be kept constant. This has the effect of suppressing variations and therefore providing a high quality UHF tuner. Moreover, the structure for realizing this is as simple as simply providing the resonant line with a rib facing the pick-up line.

[Brief explanation of the drawing]

Figure 1 is a circuit diagram of a UHF tuner. Second
3 and 3 are diagrams showing a structural example of a part of a conventional UHF tuner, and FIG. 4 is a characteristic diagram thereof. FIG. 5 is a plan view of main parts showing another conventional example. FIG. 6 is a perspective view showing one component of a UHF tuner implementing the present invention, and FIG.
The figure is a perspective view of the main parts of a UHF tuner implementing the present invention. L ₃ ... Resonant line, 5 ... Interstage secondary side tuning circuit,
9...First pick-up line, 14...Rib, d
...separation distance.

Claims (1)

[Scope of utility model registration request] A high frequency signal is picked up from a high frequency tuning circuit having a resonant line and given to an active element for mixing, and image interference is removed from the high frequency signal by adjusting the length of the pick up line and the distance between the pick up line and the resonant line. In the UHF tuner forming the trap for the resonant line L ₃
The pick-up line 9 is arranged parallel to the pick-up line, a rib of a predetermined length is provided at a desired position of the resonant line facing parallel to the pick-up line, and the pick-up line is positioned by this rib. The UHF tuner is characterized by the following.